The present invention relates generally to an electronics assembly with an improved heatsink configuration and more particularly to an electronics assembly with improved heatsinking of a power device attached to a substrate.
Electronics assemblies are formed in a wide variety of configurations for a wide variety of applications. Often, however, they are comprised of a plurality of individual electronic components mounted on a circuit board or other substrate. The individual electronic components typically communicate electronically with each other through the substrate to form a useful electronic assembly. Although the individual electronic components themselves may come in a wide variety of embodiments, one particular type is commonly referred to as a power device. Power devices are electronic components that generate heat during operation. Commonly, the thermal energy generated by these power devices must be dissipated in order for the electronic assembly to function properly. Some power devices must be kept within a predetermined thermal range in order to reliably perform their function. Others, while able to withstand larger temperature ranges, may damage the substrate or neighboring electronic components if the thermal energy is not properly dissipated.
Numerous approaches have been developed in order to dissipate heat from these power devices. Various combinations of convection and radiation transfer have been utilized to transfer the thermal energy from the power devices. One well-known and successful approach has been through the use of a heatsink device. Heatsink elements provide a thermal well to absorb the heat generated by power devices. They often take the form of large blocks of metal, or other thermal conductive material, with the capability of absorbing the thermal energy from the power devices and dissipating it over a larger surface area. The specific configuration of such heatsink devices is virtually limitless, although common embodiments such as metal blocks, cases, and heat rail brackets are well known. Although the heatsink element may be modified into a variety of forms, thermal communication between the heat sink element and the power devices often requires careful design consideration.
One approach to providing communication between the heatsink element and the power devices has been to assemble the electronic assembly such that the heatsink contacts the top of the power device wherein the power device is positioned between the heatsink element and the circuit board or substrate. Although such a configuration appears to benefit from simplicity, specific embodiments can suffer from disadvantages. In order to insure proper contact between the heatsink element and the power device, for example, clamping forces may be developed pressing the power device down onto the substrate. It is possible for these clamping forces to cause electrical shorts when the power device is pressed into the substrate. This undesirable situation may result in improper function of the electronics assembly, reduced durability of the electronics assembly, or even complete failure of the electronics assembly. In addition, since the power devices are often not the only electronic components mounted to the substrate, the heatsink element must often be designed and positioned to only contact the power devices. Improper formation or positioning during assembly can result in damage to other electronic components or electrical shorts at other locations in the electronics assembly. The tight tolerances often required in manufacturing and assembly in order to avoid electrical shorts while continuing to provide adequate thermal contact may add undesirable cost increases to the electronics assembly.
A second traditional approach to providing thermal communication between the heatsink element and the power devices has been to position the heatsink on the opposing side of the substrate from the power device. In this configuration, excessive clamping forces on the power device and interference with other electronic components may be reduced. Despite these advantages, this configuration presents its own set of disadvantages. Thermal energy generated by the power devices must be transferred through the substrate in order to reach the heatsink element. The composition and formation of many substrates can make the dissipation of large quantities of thermal energy impractical and thereby create limitations on the types of power devices utilized in the electronic assembly. Furthermore, as adequate thermal contact between the heatsink element and the substrate is required, the substrate in turn may now experience undesirable clamping forces. Careful design and assembly procedures must be undertaken to insure the heat sink does not cause electrical shorts through contact with the substrate nor damage the substrate through the clamping forces. This, too, may lead to undesirable cost increases or undesirable failure or damage to the electronics assembly.
A third known technique of providing thermal communication between the heatsink element and the power devices is capable of reducing the clamping forces and associated electrical shorts as compared to the aforementioned configurations. This approach mounts the power devices directly on the heat sink element and then provides remote electrical communication between the power devices and the substrate through the use of procedures such as wire bonding. Although this configuration may provide some advantages in clamping force reduction, it can add undesirable increases to manufacturing and assembly costs. Often, the wire bonding, and similar procedures, require machinery and additional manufacturing steps that may increase the cost of the electronics assembly undesirably. Furthermore, the use of wire bonds may not be suitable for power devices with large current communication with the substrate. These high current power devices may require a more substantial electrical pathway to the substrate than can be practically provided by wire bonding or other remote attachment techniques.
It would, therefore, be highly desirable to have an electronics assembly with a thermal dissipation configuration with reduced clamping forces, reduced electrical shorts, and broad thermal dissipation capabilities. In addition, it would be highly desirable to have an electronics assembly with a thermal dissipation configuration that could be used with high current power devices.
It is, therefore, an object of the present invention to provide an electronic assembly with a thermal dissipation configuration that reduces clamping forces while providing broad thermal dissipation capabilities. It is a further object of the present invention to provide an electronics assembly with a thermal dissipation configuration that is capable of use with high current power devices.
In accordance with the objects of the present invention, an electronics assembly is provided including a substrate having a first side, a second side, and at least one opening. At least one power device is mounted on the first side of the substrate. A heatsink element is positioned on the second side of the substrate and is in thermal communication with the at least one power device through the at least one opening.